File menu > Replace
Replace lets you substitute the geometry of one or more objects in a scene by merging objects with duplicate names. Use Replace when you want to work with less complex geometry to set up your scene and animation, and then replace it with more detailed geometry before rendering.
When you replace an object in your scene, you replace its geometry, including its modifiers, but not its transforms, hierarchy, or materials.
To replace the object with all its characteristics, use Merge.
If the object that you're replacing has instances in the scene, all of the instances are replaced with the new object.
All objects in the scene with the same name as the incoming object are replaced by that object. If you have more than one object in the scene with the same name as the incoming object, all of those objects are replaced.
See also
Procedures
To replace items:
Choose File > Replace to display the Replace File dialog.
To see more than one file type at a time, choose the All Files file type.
Select a file from which to choose replacement items.
On the Replace dialog for that file, choose a group or a replacement item. (See the following procedure.)
An alert asks if you want to replace the materials along with the objects.
If yes, the materials from the incoming objects replace the current materials.
If no, only the geometry is replaced, while the material assigned to the original object is retained.
To select objects to replace, do one of the following:
Type the name of an item, or use wildcard characters to specify multiple items that share a set of characters in their names.
Click to select single objects.
Press CTRL and click to add and remove single objects from the selection.
Press SHIFT and click to select all objects between the previously selected object and the current object.
Click All or None to select or deselect the entire list.
Interface
In the standard file selector dialog, select the gmax scene file to replace. To see more than one file type at a time, choose the All Files file type.
After you select a file, select the objects to replace in the Replace dialog. Either enter the object name or select the object from the Object List.
All/None: Selects all list items or no items.
Invert: Reverses the current list selection.
Display Subtree: Displays the objects in the list in an indented format. Clear this option and the Sort group is enable.
Select Subtree: When this option is selected, all items indented below the selected one are also selected.
Case Sensitive: Distinguishes between upper and lowercase for item names.
Sort group
Options allow you to sort the list on the left. If the Display Subtree check box is on, these options are not available.
Alphabetical: Sorts from A at the top to Z at the bottom.
By Type: Sorts by category, using the same order as the check boxes in List Types.
By Color: Sorts by object wireframe color.
List Types group
Determines which components in the scene are displayed in the list on the left: geometry, shapes, lights, cameras, helpers, and groups. Group names appear in brackets.
Note: If you turn off Groups display, only the group name is shown, in brackets. To merge an entire group, select the group and all its children.
All/None: Turns all check boxes on or off.
Invert: Reverses the current status of check boxes.